Centrifuge rotors, buckets and combinations of such buckets and rotors



A rl 9, 1968 G. D. FOX ETAL 3,377,02l CENTRIFUGE ROTORS, BUCKETS ANDCOMBINATIONS OF SUCH BUCKETS AND ROTORS 2 Sheets-Sheet L Filed May 17,1965 G. D. FOX ETAL 3,377,02l CENTRIFUGE ROTO ETS AND COMBINATIONS 2Sheets-Sheet Aprl 9, 1968 RS, BUCK I OF SUCH. BUCKETS AND ROTORS FiledMay 17, 1965 United States Patent O 3,377,021 CENTRIFUGE ROTORS, BUCKETSAND COM- BINATIONS OF SUCH BUCKETS AND ROTORS Gerald D. Fox and John E.Joyce, Quincy, Mass., and

Robert C. Leif, Los Angeles, Calif., assigno's to InternationalEquipment Company, Needham Heiglts,

Mass., a corporation of Massachusetts Filed May 17, 1965, Ser. No. 456,310 6 Claims. (Ci. 233-26) ABSTRACT OF THE DISCLOSURE Centrifuge rotorsand buckets and combinations of buckets and rotors, the buckets androtors having, respectively, detachablytmating, ball and socketconnecting por tions.

'The present invention relates to combinations of centrifuge buckets androtors of the type where the buckets are detachably connected to 'arotor to swin-g from a depending, 'vertical position into a position atright angles to the rotor aXis in response to centrifngal force. T-hein- Vention also relates to centrifuge rotors and to the buckets tor usein such combinations.

The Construction used to etiect the attachment of *buckets to centrifugerotors has 'heretofore placed limits on rotor designs and, -accordingly,on such important factors as the number of buckets that a head may carryand the speed at which it may be safely rotated without the r-isk ofbreakage. Existing constructions employ pivotal connections between thebuckets and the rotors. In one such commonly used construction, therotors have their peripheries formed with an outwardly disposed fl-angei provided with a circumferentially spaced series of vertical slots, onefor each bucket. Each bucket is provided with trunn-ions adjacent itsend that has a removable closure and at the upper end of eachbucket-receiving slot there are undercut shoulders receiving thetrunnions and pivotally confining them during centrifugation. Anyproposal to increase the strength of pivot connections leads,'=for anysize of head, to -a reduction in the number of buckets that it cancarry, to increased rotor weight, or both. The avoidance of rotorbreakage is, accordingly, troublesome and has been considered largely ametallurgcal problem.

The general objective of the present invention is to provide centrifugerotor and bucket combin-at-ions in which the connection between eachbucket and its rotor is of a ball andsocket type.

In accordance with the invention, the objective is attained 'byproviding .a centrifuge rotor and bucket for use therewith. Each bucketis of the type including a tubul ar portion closed at one end andprovided with fiange structure ad-jacent the other end, the flangestructure providing diametrically opposed portions whose faces that aredisposed towards the closed end are sphen'cal. The rotor has top andbottom faces, a plurality of spherical sdckets spaced inwardly of butadjacent its periphe-y and a slot opening upwardly into each socket, andbucket entrances through one of its faces, one entrance for each socketand associated slot. Each socket receives the flanged end of a bucketand the slot in communication with that socket receives the tubularportion thereof and is of a length 3,377,021 Patented Apr. 9, 1968 iceis 'intersected by the associated slot.

In one embodiment of the invention, the rotor has a plurality of radialslots opening through the lower part of its :periphery and itsundersurface, each slot being dimensioned to slidably receive thetubular portion of a bucket as -it swings from its position of rest intoits position of use. -Each slot has an entrance through a rotor faceadjacent the rotor axis dimensioned to receive the flanged end of abucket and is undercut to accommodate that end, each undercutterminating in a socket adjacent the periphery of the rotor forsupporting a bucket both when the rotor is at rest and when it isbrought up to speed with the bucket then at right angles to the rotoraxis, the socket and ilange being dimensoned so that together theyprovide a bucket-to-rotor connection of the ball and socket type.

'Each centrifuge rotor in -accondance with the invention is possessed ofadequate strength to ensure against 'break- 'age at rotor speeds thatare relatively high for its size and weight while providing support fora number of buckets that is relatively large for its size. This resultis due not only to the relatively 'large areas of mutual contact betweenthe rotor and its buckets -but also because the invention makes itpossible to support the buckets within 'open slots extending from pointsadjacent 'the `rotor aXs outwardly and upwardly through the lower partof its periphery, leaving the upper part thereof as an annularreinforcement for the upper parts of the sockets.

Another advantage of the ball and socket conne'ctio-n's between therotor and its buckets 'is that the slots receiving the tubular bucketportions may be shaped to permit the buckets to Swing in trailingdirections to a desred augu- Iar extent as the rotor speed increases ordecreases.

'In the -accompanying drawings, there are shown illustratve embodimentsof the invention from which these :and other of its objectives, novelfeatures, and advantages will be apparent.

In the drawings:

F-IGURE 1 is a partly sectioned, top pl=an view of a rotor tin-accordance with the invention showing the flange d end of one bucket inits socket,

FIGURE 2 is a section taken approxmately along the indicated lines 2-2of FIGURE 1 and showing buckets in side elevation,

FIGUR'E 3 is a fragnentary section of the rotor taken vertical lythrough a 'bucket-supporting socket and slot,

FIGURE 4 is a fragmentary side elevat'ion of -a rotor,

FIGURE 5 is a longitudinal section of .a bucket drawn on an increasedscale, and

FIGURE 6 is a view similar to FIGURE 4 but illustrating anotherembodiment of the invention.

The centrifuge 'bucket-s shown in the drawings are generally indicatedat 10. Each bucket 10 includes a tubular portion 1 1 that is closed atone end and has its other end counte' bore-d to provide a seat 12 for' aseal -13 and th-readed to receive a cap 14. Adjacent the capped end ofea'ch bu cke t, there is a circul'ar flange '15 whose face that isdspdscd towards the closed end there'of is spherical. As will beapparent from FIGURE 5, each tubular portion 1'1 is externally tapercdinwardly towards its closed end in order to achieve the best weightdistribution of the tube and its contents during centrfug'ation, thetaper being necessarily slight because the bucket walls 'are relativelythin and because the inside diameter of the tubular portion 1*1 isconstant.

A rotor in accordance with the invention is generally indicated at 16and is shown -as having an aXial bore 17 to receive the centrifugespindle, not shown, the bore 17 having -diametrically disposed channels18 to receive the driving pins thereof as one example of a conventionalway of securing a rotor to its drive. The ohamber in which this type ofrotor is spun may or may not be a va'cuum chamber, vacuum chambers beingcommonly used when high speeds are desired that would otherwise placeundue loads on the motors.

'The rotor 16 has a plurality of circumferentially spaced, open slots 19extending vertically from the bottom of the rotor through the lower partof its periphery. The width of the slots 19 is such that each mayaccommodate the tubular portion 1 1 of 'a bucket 10.

Each slot 19 is undercut to accommodate the flanged end of a bucket 10,the undercut being shown as starting in the un'dersurface adjacent therotor axis and terminating short of the periphery of the rotor toprovide =a se'at that is suficiently spherical to provide a socket 20for the sp'herical .face of a flange of the bucket both when the rotoris at rest and when its speed is such as to cause the buckets 10 toswing outwardly into positions in which their axes are at right anglesto the axis of the rotor 16. Each socket 20 is -also shown as slightlyelongated and downwardly inclined, say relative to a plane at rightangles to the rotor axis, so that each socket 20 may serve to securelyretain a bucket when the rotor 16 is at rest.

Reference is now made to FIGURE 2, Wherein the right hand bucket -10 hashad its stoppered and flanged end entered upwardly through the open,undercut end of a slot 19 and moved radially outwardly toward it'ssocket 20. The left hand bucket 10 is shown as ful-ly supported by itssocket so that, when the rotor is turnng rapidly enough, it will swingsmoothly outwardly into its dotted line position.

The production of rotors may be effected as with an appropriatelydimensioned spherical cutter utilizing the slots 19 as a guide for theshank of the tool, introducing the cutting head of the tool at theundersu'rface endof a slot 19 and advancing it first upwardly and thenradially outwardly and preferably downwardly at -a small angle relativeto the horizontal, say 5, to ensure bucket retention when the rotor 16is 'at rest.

A rotor in accordance with the invention is of adequate strength forhigh speed Operations since the area o'f its contact with the bucketflanges is large due to the balland-socket type of connection betweenthe buckets and their rotor.

The smooth and potentially universal motion characteristc ofball-and-socket connections also permits additional advantages incentrifugation. To enable the closed ends of the buckets 10 to trail, asis sometimes recommend, at the start of a centrifuge cycle and also whenthe rotor slows down, each slot may have its lower end slightly widenedand upwardly and inwardly tapered as 'at 19'A, see FIGURE, 6, to anextent permitting desired trailing of the buckets as the rotor isbrought up to speed or slows down. As the rotor 1 6A shown in FIGURE 6is otherwise identical to the rotor 16, it is not otherwise detailed.

We claim:

1. A centrifuge rotor for supporting buckets, each bucket of the ty peincluding a tubular portion closed at one end and provided with flangestructure adjacent its other end, the flange structure providingdametrically opposed portions whose faces that are dsposed towards saidclosed end are sphercal with respect to a common center, said rotorhaving a plurality of bucket entrance passages of circular sec't'on andof a diameter to accommodate the bucket flange structure and spaceduniformly from the center of the rotor and from each other, eachentrance passage extending into said rotor in a vertical direction andoutwardly and downwardly within the rotor in a radial direction andtermin'ating in a retaining socket comple-mental to said fiangestructure portions, and said rotor having means for each entrancepassage to receive and guide the tubular :portion of a bucket as it isp0sitioned within the rotor with its fiange structure seate'd in thepassage socket and as the bucket swings upwardly during centrifugation,each 'of said means being in the form of a radial slo't in verticalalignment with an appropriate one of said entrance passages and openingthrough the periphery and undersurface of said rotor and into thevertically aligned entrance passage and its socket, each slot, in atleast a portion thereof, slidably receiving the tubular portion of abucket and the extent of each slot being such that a bucket may beentered into a socket and swing vertically between positions of rest anduse.

2. The rotor of claim 1 in which each slot, between the position thereinof the tubular portion of a bucket in its position of rest and theposition of the tubular portion in its position of use tapers outwardlyfrom the retaining socket to enable the tubular portion to swing into atrailing position during acceleration and deceleration when the rotorspeed is below a predetermined rate of rotation to a width such that thetubular portion is maintained radial with respect to the rotor axis whenthe predetermined rotor speed is a'ttained.

'3. The rotor of claim 1 in which the entrance passages open through theundersurface of the rotor.

4. In combination, a centrifuge rotor and buckets, each bucket of thetype including a tubular portion closed at one en'd including fiangestructure adjacent its other end, the flange structure providingdiametrically opposed por tions whose faces that are disposed towardssaid closed end -are spherical with respect to a common center, and saidrotor having a plurality of bucket entrance passages of circular sectionand of a diameter to accommoda'te the bucket fiange structure and spaceduniformly from the center of the rotor and from each other, eachentr-ance 'passage extending into said rotor in a vertical direction andoutwardly and downwardly within the rotor in a radial direction andterminating in a socket complemental to said flange structure portions,and said rotor having means for each entrance passage to receive andguide the .tubular portion of a bucket as it is positioned within therotor with `its fiange structure seated in the passage socket and as thebucket swings upwardly during centrifiugation, each of said means beingin the form of a radial slot in vertical alignment with an entrance andopening through the periphery and undersurface of said rotor and intothe vertically aligned passage and its socket, each slot, in at least aportion thereof slidably receiving the tubular portion of a bucket andthe extent of each slot being such that a bucket may be entered into asocket to have a depending position of rest and swing vertically betweenpositions of rest and use, the tubular portion of each bucket extendingthrough the appropriate one of said slotswith its fiange structureseated in a socket to provide a ball and socket type of bucket torotorconnection. I

5. The combinaton of claim 4 in which each slot, between the positiontherein of the tubular portion of a bucket in its position of rest andthe position of the tubular portion in its position of use, .tapersoutwardly from the socket to enable that tubular portion to swing into atrailing position during acceleration and deceleration when the rotorspeed is below a prede'termined rate of rotation to a width such thatthe tubular portion is maintained radal w'ith respect to the rotoaxswhen the predeter- 1,839,944 1/ 1932 Barthels 233-26 X mined rotor speediS attane'd- 1,997,919 4/1935 Strezyn'ski 233 z6 6. The combnaton ofclam 4 n whch the entrance 2160411261 7/1952 slverstolpe 233 26 passagesopen through the undersurface of the rotor.

References cited 5 HENRY T. KLINKSIEK, Prmary Exam'er.

UNITED STATES PATENTS M. CARY NELSON, Exam'ner. 1,539,*102 5/1925'Alexander 233-26

